/*
 *  Copyright 1999-2004 The Apache Software Foundation
 *
 *  Licensed under the Apache License, Version 2.0 (the "License");
 *  you may not use this file except in compliance with the License.
 *  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 */

package org.apache.tomcat.util.collections;

import org.apache.tomcat.util.buf.MessageBytes;

// Originally MimeHeaders

/**
 * An efficient representation for certain type of map. The keys
 * can have a single or multi values, but most of the time there are
 * single values.
 * <p>
 * The data is of "MessageBytes" type, meaning bytes[] that can be
 * converted to Strings ( if needed, and encoding is lazy-binded ).
 * <p>
 * This is a base class for MimeHeaders, Parameters and Cookies.
 * <p>
 * Data structures: each field is a single-valued key/value.
 * The fields are allocated when needed, and are recycled.
 * The current implementation does linear search, in future we'll
 * also use the hashkey.
 *
 * @author dac@eng.sun.com
 * @author James Todd [gonzo@eng.sun.com]
 * @author Costin Manolache
 */
public class MultiMap {

    protected Field[] fields;
    // fields in use
    protected int count;

    /**
     *
     */
    public MultiMap(int initial_size) {
        fields = new Field[initial_size];
    }

    /**
     * Clears all header fields.
     */
    public void recycle() {
        for (int i = 0; i < count; i++) {
            fields[i].recycle();
        }
        count = 0;
    }

    // -------------------- Idx access to headers ----------
    // This allows external iterators.

    /**
     * Returns the current number of header fields.
     */
    public int size() {
        return count;
    }

    /**
     * Returns the Nth header name
     * This may be used to iterate through all header fields.
     * <p>
     * An exception is thrown if the index is not valid ( <0 or >size )
     */
    public MessageBytes getName(int n) {
        // n >= 0 && n < count ? headers[n].getName() : null
        return fields[n].name;
    }

    /**
     * Returns the Nth header value
     * This may be used to iterate through all header fields.
     */
    public MessageBytes getValue(int n) {
        return fields[n].value;
    }

    /**
     * Find the index of a field with the given name.
     */
    public int find(String name, int starting) {
        // We can use a hash - but it's not clear how much
        // benefit you can get - there is an  overhead
        // and the number of headers is small (4-5 ?)
        // Another problem is that we'll pay the overhead
        // of constructing the hashtable

        // A custom search tree may be better
        for (int i = starting; i < count; i++) {
            if (fields[i].name.equals(name)) {
                return i;
            }
        }
        return -1;
    }

    /**
     * Find the index of a field with the given name.
     */
    public int findIgnoreCase(String name, int starting) {
        // We can use a hash - but it's not clear how much
        // benefit you can get - there is an  overhead
        // and the number of headers is small (4-5 ?)
        // Another problem is that we'll pay the overhead
        // of constructing the hashtable

        // A custom search tree may be better
        for (int i = starting; i < count; i++) {
            if (fields[i].name.equalsIgnoreCase(name)) {
                return i;
            }
        }
        return -1;
    }

    /**
     * Removes the field at the specified position.
     * <p>
     * MultiMap will preserve the order of field add unless remove()
     * is called. This is not thread-safe, and will invalidate all
     * iterators.
     * <p>
     * This is not a frequent operation for Headers and Parameters -
     * there are better ways ( like adding a "isValid" field )
     */
    public void remove(int i) {
        // reset and swap with last header
        Field mh = fields[i];
        // reset the field
        mh.recycle();

        fields[i] = fields[count - 1];
        fields[count - 1] = mh;
        count--;
    }

    /**
     * Create a new, unitialized entry.
     */
    public int addField() {
        int len = fields.length;
        int pos = count;
        if (count >= len) {
            // expand header list array
            Field tmp[] = new Field[pos * 2];
            System.arraycopy(fields, 0, tmp, 0, len);
            fields = tmp;
        }
        if (fields[pos] == null) {
            fields[pos] = new Field();
        }
        count++;
        return pos;
    }

    public MessageBytes get(String name) {
        for (int i = 0; i < count; i++) {
            if (fields[i].name.equals(name)) {
                return fields[i].value;
            }
        }
        return null;
    }

    public int findFirst(String name) {
        for (int i = 0; i < count; i++) {
            if (fields[i].name.equals(name)) {
                return i;
            }
        }
        return -1;
    }

    public int findNext(int startPos) {
        int next = fields[startPos].nextPos;
        if (next != MultiMap.NEED_NEXT) {
            return next;
        }

        // next==NEED_NEXT, we never searched for this header
        MessageBytes name = fields[startPos].name;
        for (int i = startPos; i < count; i++) {
            if (fields[i].name.equals(name)) {
                // cache the search result
                fields[startPos].nextPos = i;
                return i;
            }
        }
        fields[startPos].nextPos = MultiMap.LAST;
        return -1;
    }

    // workaround for JDK1.1.8/solaris
    static final int NEED_NEXT = -2;
    static final int LAST = -1;

    // -------------------- Internal representation --------------------
    final class Field {
        MessageBytes name;
        MessageBytes value;

        // Extra info for speed

        //  multiple fields with same name - a linked list will
        // speed up multiple name enumerations and search.
        int nextPos;

        // hashkey
        int hash;
        Field nextSameHash;

        Field() {
            nextPos = MultiMap.NEED_NEXT;
        }

        void recycle() {
            name.recycle();
            value.recycle();
            nextPos = MultiMap.NEED_NEXT;
        }
    }
}
